1. Field of the Invention
This invention relates to a relay server, a method of controlling the operation of the relay server and a program for controlling the operation of the relay server.
2. Description of the Related Art
A data transmitting server or the like for transmitting data requires that security be enhanced by restricting external access. Various methods of enhancing security are available. For example, one method connects a data transmitting server and another server by a private line and performs data communication utilizing the private line. Such an arrangement provides very robust security but involves a great deal of labor and very high cost. Further, although security is relatively high in a VPN (Virtual Private Network) that utilizes a router, this expedient requires detailed setting of a firewall and therefore is labor-intensive. Although there is an arrangement in which a software VPN module is placed in front of the data transmitting server, security declines because it is required to open the firewall port.
There is also a connection support server for connecting a requesting terminal and a responding terminal (see the specification of U.S. Pat. No. 3,964,266). In this arrangement a TCP connection from the responding terminal is maintained and data for maintaining the TCP connection is transmitted periodically from the connection support server to the responding terminal. A drawback, however, is that the data for maintaining the TCP connection must be transmitted periodically.